Various proposals have been made to improve the magnetic flux of the receiver, or loudspeaker, of a handset, so as to improve the coupling with a hearing aid. One proposal is to provide a flux coil positioned inside around the receiver. Such an arrangement causes problems in that it is desirable to have as large a diameter receiver diaphragm as possible in the recess in the handset provided therefor. Positioning of a flux coil inside around the receiver requires that the receiver is reduced in diameter, to provide room for the flux coil. One result of this is that if the user of a telephone, not using a hearing aid, moves the receiver away from the ear--to reduce the loudness for example--then there is a greater loss in hearing at the lower frequencies than would normally be experienced with a receiver having a larger diameter diaphragm.
Also, it is convenient to be able to use whichever receivers are available and suitable at any time, without having to modify the receivers. Modification is expensive and inconvenient.